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 24 cacti and sun DHJanzen100335.jpg high resolution
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| Cacti are well known desert plants (in the New World - any cactus you see, other than one epiphytic cactus in Madagascar, in the Old World has been introduced by people). This is actually not so much because they have to have a dry climate (though there is an element of this because many cacti are more susceptible to fungal diseases in wet habitats than in dry habitats), as because they need unobstructed insolation (and note that their branching pattern - a few large branches - does not lend itself to inter-crown competition with other angiosperms). You do not expect to meet cacti in a forest. Here, for example, these columnar cacti are growing on the hot dry rocks of the forest in Costa Rica where it meets the sea (to the right). Here they are in a habitat where the less dryness-resistant ordinary tropical trees cannot survive, leaving a space that cacti can occupy. There is another place in tropical forests are found - growing on exposed upper tree branches in the canopy as epiphytes. Here, the world is very dry (between rains) but also very sunny. | ||
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